It is known, for example from French Pat. No. 2,587,895, to secure a removable dental prosthesis magnetically to an anchor face of a ferromagnetic body implanted in a jaw by means of an attachment system comprising a saliva-resistant cushioning mass secured in the prosthesis and forming a pocket open toward the anchor face, a ferromagnetic and saliva-resistant shell seated in the pocket and open toward the face, and a permanent magnet fixed in the shell and having a magnet face confronting the anchor face. The permanent magnet is of relatively great strength and of a material corrosible by saliva.
The shell typically leaves the magnet face exposed and, in order to protect it, it is covered with a layer about 3 mm thick of a protective material such as an acrylic resin. As this material is not magnetically attractable, it forms in effect an air gap between the magnet face and the anchor face. The magnetic attraction is therefore severely limited, so that the practice is to reduce the thickness of the protective coating in order to obtain maximum hold. This of course leaves the magnet relatively poorly protected and, if a leak occurs, the magnet quickly corrodes so that the denture needs to be repaired or replaced.